I always encourage my clients to utilize the toilet during labor. My saying is, "When nature calls, sit through at least 3 contractions". The body instinctually relaxes when sitting on the toilet. This is a place where sphincters are used to opening and sphincters opening is crucial for labor progress! For more about Sphincter Laws, be sure to read Ina May's book.
To get an idea of how to make laboring on the toilet a little more comfortable, check out this wonderfully written article at Baby Bump Services.